535 / 1002
BRAKES
16
6.9 ABS COMPONENTS
6.9.1 ABS 9 ELECTRONIC CONTROL UNIT
/ HYDRAULIC CONTROL UNIT (ECU / HCU):
General
This is an Electro-hydraulic device for reducing,
holding & restoring pressure to one or more wheel
brake, independent of the brake pedal effort
applied by the driver.
It consists of:
i. An Electronic Control Unit (ECU) and
ii. A Hydraulic Control Unit (HCU).
(i) ECU:
Solid state electronic device containing computer
functions, sensor signal processing circuits, output
device drives for the various ABS valves &
components and Failure Detection Logic.
The ECU is integrated in a single package with the
Hydraulic Control Unit (HCU). It has 2 Micro
controllers, which utilize the same program for
independent data processing and monitoring
functions. One of the Micro controllers has an
EEPROM to retain memory data in case battery
supply is interrupted. The EEPROM is a non-
volatile data storage device employed to store
error codes, which can be read out for diagnosis.
When an error is encountered ABS switches itself
off and triggers the ABS warning lamp. An
independent module controls the solenoid valve
relay and return pump motor.